2. 外语
  3. The word "laser" was coined as an acronym for Light Amplification by the Stimulated Emission of Radiation. Ordinary light, from

The word "laser" was coined as an acronym for Light Amplification by the Stimulated Emission of Radiation. Ordinary light, from

admin2010-03-26  39
问题     The word "laser" was coined as an acronym for Light Amplification by the Stimulated Emission of Radiation. Ordinary light, from the Sun of a light bulb, is emitted spontaneously, when atoms or molecules get rid of excess energy by themselves, without any outside intervention. Stimulated emission is different because it occurs when an atom of molecules holding onto excess energy has been stimulated to emit it as light.
    Albert Einstein was the first to suggest the existence of stimulated emission in a paper published in 1917. However, for many years physicists thought that atoms and molecules always were much more likely to emit light spontaneously and that stimulated emission thus always would be much weaker. It was not until after the Second World War that physicists began trying to make stimulated emission dominate. They sought ways by which one atom or molecule could stimulate many others to emit light, amplifying it to much higher powers.
    The first to succeed was Charles H. Townes, then at Columbia University in New York. Instead of working with light, however, he worked with microwaves, which have a much longer wavelength, and built a device he called a "maser", for Microwave Amplification by the Stimulated Emission of Radiation. Although he thought of the key idea in 1951, the first maser was not completed until a couple of years later. Before long, many other physicists were building masers and trying to discover how to produce stimulated emission at even shorter wavelengths.
    The key concepts emerged about 1957. Townes and Arthur Schawlow, at Bell Telephone Laboratories, wrote a long paper outlining the conditions needed to amplify stimulated emission of visible light waves. At about the same time, similar ideas crystallized in the mind of Gordon Gould, then a 37-year-old graduate student at Columbia, who wrote them down in a series of notebooks. Townes and Schawlow published their ideas in a scientific journal, Physical Review Letter, but Gould fried a patent application. Three decades later, people still argue about who deserves the credit for the concept of the laser.
Why was Townes’ early work with stimulated emission done with microwaves?
选项 A、He was not concerned with light amplification.
B、It was easier to work with longer wavelengths.
C、His partner Schawlow had already begun to work on laser.
D、The laser had already been developed.
答案B
解析 推理判断题。文章第三段讲到了Townes用较长的微波来研究激光而不是昔通光，但是他成功后，好多人(包括他自己)都在用波长更短的光线来研究激光，直到1957年，理论才明朗起来，这就暗示了B“用较长的微波来研究要容易一些”这一项的意思。A为“他对于增强光线不感兴趣”；C为“他的搭档Schawlow 已开始研究激光了”，文中没有提到：D为“激光早已研制出来了”，从文中可知，那时激光还未研制出来，所以D也不符合题意。
转载请注明原文地址:https://kaotiyun.com/show/T9OK777K
0

大学英语六级

相关试题推荐
随机试题
最新回复(0)